/**
 * Copyright 2009 Takahiko Ito
 *
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.unigram.oluolu.ngram;

import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

/**
 * 
 */
public class FrequentNGramReducer extends
        Reducer<Text, IntWritable, Text, LongWritable> {

    /** minimum frequency. */
    private long minimumSupport;

    /**
     * Reduce method.
     * @param key query string
     * @param values query frequencies
     * @param context flush key and value
     * @throws IOException -
     * @throws InterruptedException -
     */
    @Override
    protected final void reduce(final Text key,
            final Iterable<IntWritable> values,
            final Context context) throws IOException,
            InterruptedException {

        int sum = 0;

        for (IntWritable value : values) {
            sum += value.get();
        }
        if (sum >= minimumSupport) {
            context.write(key, new LongWritable(sum));
        }
    }

    /**
     * Setup.
     * 
     * @param context used to extract needed system properties
     */
    @Override
    protected final void setup(final Context context) {
        Configuration jc = context.getConfiguration();
        this.minimumSupport = jc.getLong(
                NgramConstants.NGRAM_MINIMUM_SUPPORT,
                NgramConstants.DEFAULT_NGRAM_MINIMUM_SUPPORT);

    }
}
